1. Field of the Invention
The present invention relates to a method of and an apparatus for scaling up and down an input video image and displaying the resultant video image on a display device.
2. Description of the Related Art
In some cases, it is required to display video images generated by a computer on another display device, such as a liquid-crystal projector. In such a case, the computer should generate video signals according to the resolution of the display device. In the description of this specification, the term "resolution" implies both a number of dots (that is, a number of pixels) in a horizontal direction of a video image and a number of lines (that is, a number of scanning lines) in a vertical direction. The number of dots in the horizontal direction is referred to as the horizontal resolution, whereas the number of lines in the vertical direction is referred to as the vertical resolution.
The resolution and the number of tones of a video image generated by a computer are restricted by the capacity of a video RAM (VRAM) in the computer. The number of tones is reduced for a display with a greater resolution (that is, a larger screen size), and increased for a display with a smaller resolution. When the display device has a significantly large screen size, it may be impossible to make the resolution of a video signal generated by the computer coincident with the resolution of the display device. The similar problem arises when a video image generated by a device other than the computer (for example, a television image) is displayed on a display device other than a television receiver.